A number of special purpose analyzers are available for the measurement of various analytes in human body fluid samples. In the past, such analyzers were often adapted to test for a single analyte in a patient sample and may have required extensive operator actions to perform an analysis. For example, the operator might be required to perform manual pipetting of patient sample and reagents into a test chamber or cuvette, manual timing of the reaction, and the manual reading of an arbitrary value from the analyzer that is then compared to previously generated calibration values to obtain a final result. As is readily apparent, largely manually operated analyzers are not suitable for either a large number of patient sample analyses or to performing an analysis in a limited amount of time.
In order to meet the increasing demand for the routine testing of a growing number of analytes as well as for the reduction in overall testing costs and the skill required of the technician/operator, several analyzers are currently available which are partially or fully automated. A typical automated analyzer can analyze a single fluid sample for a plurality of analytes with little or no intervention on the part of an operator.
The number of different analytes or chemistries that an automated clinical analyzer can analyze is often termed the "menu" of chemistries available on the analyzer. An automated analyzer may be designed, for example, to analyze a limited menu of basic chemistries that represent the bulk of the work load in a clinical chemistry laboratory, such as glucose, creatinine, sodium, potassium and the like. On the other hand, other analyzers may offer a much larger menu, sometimes ranging up to 50 or 60 different chemistries. Many of such chemistries may represent relatively low volume chemistries, that is, ones that are required on an infrequent basis as compared to the basic chemistries mentioned above.
Each chemistry run on an analyzer generally requires its own unique reagent or combination of reagents. Although it would be desirable to maintain all of the reagents on the analyzer for each of the chemistries on the menu, most large menu analyzers do not have the storage capacity to do so. Instead, reagents for a subset of the menu are stored on the analyzer at one time. When an analysis is to be run that requires reagents that are not presently stored on board the analyzer, the reagents must be placed onto the analyzer before the analysis is run. If the reagent storage area on analyzer is already full, then reagents for a chemistry not in use are removed and the reagents for the new chemistry are installed in their place. With such an approach, it is desirable that the analyzer maintain as many reagents on board as possible and, further, that reagents be easily removed and replaced so that analyzer down time and operator time can both be minimized.
It is known in the art to use reagent cartridges on automated clinical analyzers to increase the ease with which reagents are handled and decrease the time required to reconfigure the chemistries on board the analyzer. Such cartridges may contain all of the various reagents required for a particular chemistry and may be configured to fit onto a reagent storage rack or wheel within the analyzer.
An example of this type of cartridge is used on the Spectrum.TM. analyzer manufactured by the Diagnostic Division of Abbott Laboratories in Irving, Texas. The Spectrum analyzer employs a molded plastic reagent cartridge generally in the form of a truncated wedge and containing several chambers for the various reagents required for a chemistry. The reagent cartridge fits into an annular well within a reagent storage wheel on the analyzer and each cartridge is accessed by one or more automatic probes that dip into the cartridge chambers.
The reagent cartridge used on the Spectrum analyzer, however, has several disadvantages which are characteristic of reagent cartridges for automated analyzers. The Spectrum analyzer reagent cartridge has integrally formed common walls between the adjacent reagent chambers. It is believed by Applicant herein that reagents stored in adjacent chambers tend to become contaminated due to migration of the reagents through the common chamber walls. Reagent migration is a problem that has been heretofore unrecognized in the art. It is important because contaminated reagents can give spurious test results which may be life threatening. Reagent migration can also decrease the storage life of the reagents, thus increasing analyzer operating costs. The increased operating costs are particularly apparent where the reagents stored in a cartridge are used infrequently and must be stored for a relatively long period of time until consumed.
From an operator's standpoint, the Spectrum analyzer reagent cartridge is difficult to remove from the instrument. Although the cartridge must be lifted upwardly from the storage wheel, the cartridge provides no convenient means by which it may be grasped from above.
Further, the cartridge and the wheel which receives the cartridge provide no sure indication that the cartridge is properly seated in the wheel. Thus, a misaligned cartridge or debris in the storage wheel can cause improper indexing between the cartridge and the wheel. Since the cartridges are each accessed by automatic probes inserted a predetermined distance into the cartridges, inadequate or improper indexing may result in a collision between the probe tip and the bottom of the cartridge. Although such collisions can be avoided by decreasing the insertion depth of the probe into the cartridge, the resulting distance between the inserted probe tip and the bottom of the cartridge causes unused reagent to be left in the cartridge, further decreasing the cost effectiveness of the automated analyzer. Also, a misaligned cartridge may incorrectly access openings with respect to the probe, causing the probe to impact the cartridge and damaging both the probe and cartridge.
Also, the Spectrum analyzer cartridge have been assembled using what is believed to have been ultrasonic welding which may not form a sure, uniform seam. The result is a cartridge which is costly to manufacture and which has a tendency to leak.